Power split transmission structure

ABSTRACT

A power split transmission structure has at least three interfaces to direct driving power from a drive to at least one output in order to supply the driving power to connected consumers. It comprises at least two variator paths which each comprise a summation gearbox communicating with an electric or hydraulic machine via a mechanical and a non-mechanical path in order to modify torque, speed or both of the driving power. A control device regulates the summation gearbox of each of the variator paths. A power electronics system or hydraulic control device is connected to the electric or hydraulic machine of each of the variator paths. The transmission structure directs the driving power via the variator paths such that the electric or hydraulic machine of each variator path is operable in a generator or motor mode in order to compensate for a power shortfall or a power oversupply at at least one outlet of the transmission structure.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to German application No. DE102018215684, filed Sep. 14, 2018, which is incorporated herein in itsentirety.

STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE DISCLOSURE

The disclosure relates to a power split transmission structure to directdriving power from a drive to at least one output supplying connectedconsumers.

BACKGROUND OF THE DISCLOSURE

Continuously variable power split transmission units are to be found inconstruction machines and agricultural work machines, for exampletractors, according to the current prior art in particular frequently inthe premium sector, and are realized as hydraulically/mechanically powersplit transmissions. The power flow is split, in this connection, into amechanical path, which is run steadily via one or multiple planetarygear sets, and into a hydrostatic path, in which the power is run via ahydrostatic variator, by way of which continuously variable adjustmentof the gear ratio is able to be performed.

DE 19749074C2 and DE 102012204477A1 disclose continuously variable powersplit transmission units where the variable path is realized in eachcase as an electric variator. In the case of such electromechanicaltransmissions, both mechanical and electric power is utilized as drivingpower.

A different direction of development in the case of constructionmachines and agricultural work vehicles consists in the design of asecond on-board electrical system, which is in addition to the existingon-board electrical system of the machine and is operated at a highernominal voltage, by way of which electric consumers, which require sucha higher nominal voltage for their operation, are able to be driven. Theelectric consumers can be arranged both on the machine per se and on anattachment device. The additional second on-board electrical system isconventionally generated on the machine by its own generator systemwhich is provided for this purpose. However, additional product costsarise in this connection and the overall degree of efficiency is reducedas a consequence of the additional components.

SUMMARY OF THE DISCLOSURE

In one aspect, the disclosure provides a power split transmissionstructure including at least three interfaces to direct driving powerfrom a drive to at least one output of the interfaces in order to supplythe driving power to connected consumers. At least two variator pathseach comprise a summation gearbox communicating with an electric orhydraulic machine via a mechanical and a non-mechanical path in order tomodify torque, speed or both of the driving power. A control deviceregulates the summation gearbox of each of the variator paths, and apower electronics system or a hydraulic control device is connected tothe respective electric or hydraulic machine of each of the variatorpaths. The transmission structure directs the driving power via thevariator paths such that the electric or hydraulic machine of each ofthe variator paths is operable in a generator or motor mode in order tocompensate for a power shortfall or a power oversupply at the at leastone outlet of the transmission structure.

The details of one or more example embodiments are set-forth in theaccompanying drawings and the description below. Other features andadvantages will become apparent from the description, the drawings, andthe claims.

BRIEF DESCRIPTION OF THE DRAWINGS

At least one example of the present disclosure will hereinafter bedescribed in conjunction with the following figures:

FIG. 1 shows an example of the transmission structure with a firstexample of a power flow;

FIG. 2 shows another example of the transmission structure with afurther example of a power flow;

FIG. 3 shows another example of the transmission structure with afurther example of a power flow;

FIG. 4 shows another example of the transmission structure with afurther example of a power flow; and

FIG. 5 shows another example of the transmission structure with afurther example of a power flow.

Like reference symbols in the various drawings indicate like elements.For simplicity and clarity of illustration, descriptions and details ofwell-known features and techniques may be omitted to avoid unnecessarilyobscuring the example and non-limiting embodiments of the inventiondescribed in the subsequent Detailed Description. It should further beunderstood that features or elements appearing in the accompanyingfigures are not necessarily drawn to scale unless otherwise stated.

DETAILED DESCRIPTION

Embodiments of the present disclosure are shown in the accompanyingfigures of the drawings described briefly above. Various modificationsto the example embodiments may be contemplated by one of skill in theart without departing from the scope of the present invention, asset-forth the appended claims.

This disclosure may provide a transmission structure which enablesimproved efficiency, multiple outputs of the transmission system havingto be supplied at the same time. The transmission structure may have atleast three interfaces in the form of inputs or outputs in order todirect driving power from a drive to at least one output in order tosupply connected consumers. In this case, the transmission structurecomprises an electric or hydraulic machine for converting the drivingpower and at least two variator paths, which each comprise a mechanicaland an electric path, in order to modify torque and/or the speed,wherein the variator paths each comprise an electric or hydraulicmachine and a summation gearbox, for summation of the power from amechanical path and from a non-mechanical path. In addition, thetransmission structure comprises a control device for regulating thesummation gearbox, wherein the transmission structure additionallycomprises a power electronics system/hydraulic control device which isconnected to the electric or hydraulic machines. The transmissionstructure directs the driving power via the variator paths such that theelectric/hydraulic machines are able to be actuated in generator ormotor mode in order to compensate for a power shortfall or a poweroversupply at at least one outlet of the transmission structure.

As a result of the arrangement of the transmission structure and the useof at least two variators, the overall efficiency is able to beincreased. The driving power, which is mostly made available by aninternal combustion engine, is converted into electric or hydraulicpower in a first electric/hydraulic machine and made available to thepower electronics system which distributes it to the variator pathsaccording to the requirements thereof or is even able to re-convert itinto mechanical driving energy. The transmission structure enables veryprompt adaptation of the performance characteristics of the vehicle sothat it is possible to react immediately to modified driving conditions.This makes it possible to avoid a shortage in driving power orelectric/hydraulic power for instance in the case of towed work devices.

In a further embodiment, the transmission structure can comprise one ormultiple additional transmissions with a variable gear ratio in at leastone variator path.

The transmission structure, in this connection, can be provided with anynumber of further variators, it also being possible, as a result, forfurther inputs and/or outputs of the transmission structure to beprovided. As the requirements concerning agricultural work machinesalways increase, the transmission structure, in this connection, is ableto be adapted flexibly to modified conditions.

In the case of a further development, the power electronics system canhave an external supply connection, the supply connection being able toconsume and/or output power.

The transmission structure can consequently comprise an electricconnection which is supplied as needed by the power electronics systemand serves for the purpose of supplying a connected device, for examplea device trailed by the work machine, with electric power. The electricpower which is needed by a trailed device can be subject to temporalfluctuations, for instance as a result of different ground conditions,inclines or work requirements. Depending on the implementation of thedevice, recovery of electric power can also be provided, for example inthe case of a braking operation. The fluctuations are able to beintercepted or eliminated by the transmission structure by electricpower being directed to the output or being converted coming from theoutput and/or being directed to other consumers inside the transmissionstructure as a result of using and actuating the electric/hydraulicmachines together with the power electronics system.

In one example implementation, the transmission structure can comprisean output which is operatively connected to a power take off shaft suchthat power is able to be output to the power take off shaft or consumedby the power take off shaft.

The power take off shaft is subject to temporal fluctuations in thepower requirement. This can occur as a result of the lie of the land,the speed of the vehicle or of the work machine and as a result of thechanging ground conditions. The power fluctuations can be compensatedfor or intercepted by the transmission structure. Smoother working anduniform power requirement of the drive is made possible. Power is ableto be directed into the transmission structure and from there run tofurther outputs by the power consumption from the power take off shaft.

In the case of a further example, an output of the transmissionstructure can be operatively connected to a travel drive such that poweris able to be output to the travel drive or consumed by the transmissionstructure.

The travel drive, which serves for the purpose of driving the workmachine, can be connected or provided at an output of the transmissionstructure. The supplying of the travel drive with driving power can becontrolled by the transmission structure, a power shortage at the traveldrive being able to be eliminated and/or to be avoided entirely as aresult even where the speed remains constant or the drive motor ispowered by the additional introduction of driving power by theelectric/hydraulic machines. In addition, driving power can be consumedby the transmission structure, for example when braking, and can beconverted into electric/hydraulic energy by the electric/hydraulicmachines, this being able to be used, in turn, for supplying a furtheroutput with power.

In another example implementation, the transmission structure cancomprise an energy store which is used for compensating for a powershortfall or power oversupply.

In the case of a further development, an output of the transmissionstructure can be connected to a hydraulic pump or a fan.

A further aspect of the disclosure relates to a method for controlling apower split transmission structure in order to direct driving power froma drive to at least one output in order to supply connected consumers.The transmission structure comprises at least two variator paths inwhich driving power is varied via a mechanical and an electric path,wherein the transmission structure comprises a power electronics system,and the method actuates the power electronics system and the electricmachines at the same time in such a manner that fluctuations in thepower supply of the consumers are compensated for by the electricmachines.

In the case of a further development, each variator path is able to beactuated individually in order to direct power from one output to afurther output such that power is able to be split for each output.

In a further example, the transmission structure can consume powerthrough at least one output and/or direct it to a further output orconvert it into electric/hydraulic power.

The following describes various implementations of a transmissionstructure for directing power from a drive machine to one or more powerconsuming devices. The following examples are described in the contextof a mechanical-electrical application in which power takes, and isconverted between, mechanical and electrical forms. It should beunderstood that the transmission structure may also be implemented inmechanical-hydraulic applications in which power takes, and is convertedbetween, mechanical and hydraulic forms. As such, reference below tooperational power electronics and motor generator machines may beunderstood to contemplate hydraulic control systems/devices andhydraulic motors or other hydraulic machines.

A transmission structure 10 is supplied with primary power by a vehicledrive 15. FIG. 1 shows the power flow by way of arrow symbols. As anexample, the number of arrows represents the power for the respectivepath in the transmission structure 10. The power paths, including oralso referred to herein as “variator paths” having mechanical andnon-mechanical paths, are shown by solid lines, on which, in turn, thearrows for the power are marked. Positions at which the power pathscross one another provide points of intersection. These can beimplemented structurally by spur gear toothing or further usualstructures. It should be noted that while single lines are shown in thefigures to represent all of the power paths, the lines may eachrepresent different power formats (e.g., mechanical or non-mechanicalpower) or include multiple power paths of the same or different (e.g.,mechanical and non-mechanical) power formats. Moreover, the power pathsmay include power that flows (mechanically or non-mechanically) directlybetween components in which case such power is not represented in thefigures by one or more designated lines.

In the illustrated example, power paths connect the drive 15 tosummation gearboxes 20, 30 and to a motor generator, which convertselectric power into mechanical power, or vice versa, during engineoperation. The summation gearboxes 20, 30 may be regulated by one ormore control devices, such as control devices 21, 31, respectively,which may be implemented in various ways, including electronically orhydraulically controlled hardware, such an electronic control devicehaving one or more processors executing program code stored on memorycomponents to control one or more actuators associated with thesummation gearboxes 20, 30.

The illustrated transmission structure 10 comprises two summationgearboxes 20 and 30. Summation gearboxes can be realized, for example,as planetary gearing. Each interface of the planetary gearing isconnected, in this case, to a branch of the power path. The uppersummation gearbox 20 in FIG. 1 is connected to the drive 15, through aninput 14 of the interface to which the drive 15 is coupled, via a powerpath A₁ and at the same time via a power path A₂ to the furthersummation gearbox 30. A second power path B₁ connects the summationgearbox 20 to a motor generator 46. A third power path C₁ connects thesummation gearbox 20 to an output 22 which, in this example, can be theoutput for driving a connected consumer 23, such as a power take offshaft.

The second summation gearbox 30 is connected to the drive 15 through theinput 15 and by way of a second power path B₂ to a motor generator 48and by way of a third power path C₂ to an output 32 of the transmissionstructure 10 which can power a connected consumer 33 in the form of atravel drive.

In addition, a system of power electronics 40 is present whichcommunicates with the motor generators 44, 46, 48 and is able totransfer and control electric power between the motor generators 44, 46,48. The power electronics system 40 is additionally connectedelectrically via a power path C₃ to a further output 42 of thetransmission structure 10 so that electric power is able to be output atthat output to another connected consumer 43.

Four arrows in FIG. 1 show a mechanical power input on a power path A₀,which is made available by the drive 15. The power input is divided intothe power path A₁ to the summation gearbox 20 and the power path A₂ tothe summation gearbox 30 at the subsequent junction on the power path.At the summation gearbox 20, the control device using the powerelectronics system 40 splits off part of the power input, shown by anarrow symbol, and converts it into electric power in the motor generator46. The electric power is directed on to the motor generator 48 by thepower electronics system and there is once again converted intomechanical power and is run into the summation gearbox 30 via the powerpath B₂. In the summation gearbox 30, the additional power is added tothe mechanical power, which is generated by the drive 15, and is outputat the output 32 to the travel drive via power path C₂. The amount ofpower is shown symbolically by three arrow symbols. The transmissionstructure 10 can be used to cover short-term requirements of the traveldrive so that there is no shortage of driving power.

FIG. 2 shows the transmission structure 10 with a further concept of thepower supply. The power input by the drive 15 is split so that one part,shown by one arrow symbol, is directed to the summation gearbox 20 viapower path A₁ and three parts are directed to the summation gearbox 30via power path A₂. The summation gearbox 30 is actuated in such a mannerthat one part of the power is delivered via power path B₂ to motorgenerator 48 where it is converted into electric power and run to themotor generator 46. The remaining two parts are made available via powerpath C₂ to the output 32 for travel driving by the summation gearbox 30.The motor generator 46 converts the electric power into mechanical poweragain, this then being added via power path B₁ to the one power part inthe summation gearbox 20. The resultant two power parts are supplied tothe output 22 via power path C₁ for driving the power take off shaft.This shows how two outputs are able to be supplied with power by thetransmission structure 10, a short-term diversion of the power beingmade possible.

FIG. 3 shows the symbolic four power parts coming from the drive 15being split in such a manner that three parts are directed via powerpath A₂ to the summation gearbox 30 and one power part to the motorgenerator 44 via power path A₃. The motor generator 44 converts themechanical power correspondingly into electric power, which is run tothe motor generator 46 controlled by the power electronics system 40. Inaddition, one part of the mechanical power in the summation gearbox 30is split off and directed to the motor generator 48 via power path B₂.There this is then also converted into electric power, this beingdirected together with the power part from the motor generator 44together to the motor generator 46 and after conversion into mechanicalpower is run back via power path B₁, the summation gearbox 20 and powerpath C₁ to form a part at the output 22 for supplying the power take offshaft and to form a part at the summation gearbox 30 via power path A₁.In this connection, the power not required is able to be diverted fordriving the power take off shaft so that further components are able tobe supplied by the transmission structure 10.

FIG. 4 shows how, for example, all outputs 22, 32, 42 are able to besupplied with power at the same time. In this connection, the power isfirst of all split in such a manner that two parts are directed in eachcase to the summation gearboxes 20, 30 via power paths A₁ and A₂. Thesummation gearboxes 20, 30 run via power paths B₁ and B₂ one part ineach case to the assigned motor generators 46, 48, which convert it intoelectric power. The power electronics system controls the summation ofthe power parts and supplies them to the output 42 via power path C₃ foran external electric power supply.

FIG. 5 shows in a further example that the transmission structure makesit possible to direct the power by the power electronics system 40 fromone summation gearbox to the other summation gearbox in order to cover apower requirement at one of the outputs. In the example shown, one partof the mechanical power is split off in the summation gearbox 20, asreceived via power path A₁, and run via power path B₁ to the motorgenerator 46 and the power electronics system 40. Finally, the powerpart in the summation gearbox 30 from via power path A₂ is added againto the remaining part of the mechanical power via power path B₂ anddirected via power path C₂ to the output 32 for the travel drive. Powerfrom power path A₃ provides to the motor generator 44, which may bedirected to the output 42 via power path C₃. It is possible to switch,in particular, between the provision according to FIG. 4 and to FIG. 5depending on the power requirements present at the outputs so that animmediate reaction to the loads that are present is made possible.

In a mode of the transmission structure in which power is output to thetransmission structure 10 from the outputs, the power is able to bedirected to the motor generators by the summation gearbox and recovered.The electric power is able to be stored for later use by an energy store41. In the case of an additional output of electric power for themechanical performance of the internal combustion engine, it is alsopossible to obtain a so-called boost function at the outputs whichprovides a short-term power boost in order to cover a load peak.

As a result of the proposed transmission structure 10, the number ofmechanical components is able to be reduced compared to a conventionaltransmission structure as a through-transmission of mechanical powerdoes not have to be obtained in full for each output. The components arealso able to be realized at the same time, in this case, in a smallersize so that the weight is able to be reduced.

As a result of the reduction in components and in the component sizes,the complexity of the transmission structure decreases at the same time,maintenance being able to be carried out at less expenditure.

As used herein, the singular forms “a”, “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The description of the present disclosure has been presented forpurposes of illustration and description, but is not intended to beexhaustive or limited to the disclosure in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of thedisclosure. Explicitly referenced embodiments herein were chosen anddescribed in order to best explain the principles of the disclosure andtheir practical application, and to enable others of ordinary skill inthe art to understand the disclosure and recognize many alternatives,modifications, and variations on the described example(s). Accordingly,various embodiments and implementations other than those explicitlydescribed are within the scope of the following claims.

What is claimed is:
 1. A power split transmission structure, comprising:at least three interfaces to direct driving power from a drive to atleast one output of the interfaces in order to supply the driving powerto connected consumers; at least two variator paths which each comprisea summation gearbox communicating with an electric or hydraulic machinevia a mechanical and a non-mechanical path in order to modify torque,speed or both of the driving power; a control device for regulating thesummation gearbox of each of the variator paths; and a power electronicssystem or a hydraulic control device connected to the respectiveelectric or hydraulic machine of each of the variator paths; wherein thetransmission structure directs the driving power via the variator pathssuch that the electric or hydraulic machine of each of the variatorpaths is operable in a generator or motor mode in order to compensatefor a power shortfall or a power oversupply at the at least one outletof the transmission structure.
 2. The transmission structure of claim 1,wherein the power electronics system has an external supply connection,and the supply connection is able to consume or output power.
 3. Thetransmission structure of claim 1, wherein the at least one output ofthe transmission structure is operatively connected to a power take offshaft such that power is output to the power take off shaft or consumedby the power take off shaft.
 4. The transmission structure of claim 1,wherein the at least one output of the transmission structure isoperatively connected to a drive output such that power is output to thedrive output or consumed by the transmission structure.
 5. Thetransmission structure of claim 1, further comprising an energy store,for compensating for a power shortfall or a power oversupply.
 6. Thetransmission structure of claim 1, wherein the at least one output ofthe transmission structure is connected to a hydraulic pump or to a fan.